1. Field of the Invention
The invention relates to signal transfer systems, and more particularly to a signal transfer system with an Inter Integrated Circuit (I2C) bus.
2. Description of the Related Art
An I2C bus is a universal bus standard for integrated circuit (IC). An I2C bus is a two-lined serial bus standard invented by Philips Company, wherein a serial clock (SCL) and a serial data (SDA) are utilized to define receiving and transmitting data between ICs.
FIG. 1 is a schematic diagram illustrating the conventional operation of an I2C bus between ICs. Each IC 110 and 120 has a SCL pin and a SDA pin, wherein the SCL pins of IC 110 and 120 are coupled together through a transmission line 130, and the SDA pins of IC IC 110 and 120 are coupled together through a transmission line 140. IC 110 is a master IC and IC 120 is a slave IC, wherein the control commands from IC 110 is sent to IC 120 via the transmission lines 130 and 140.
However, logic level interference is possible with the SCL signal and SDA signal sent from IC 110, e.g. high logic level is decreased to low logic level, when an operational voltage of the IC 110 is unstable. At this time, if IC 110 still sends the control commands to IC 120 through the transmission lines 130 and 140, IC 120 may operate with incorrect I2C commands due to the interference.
Therefore, a signal transfer system is desired to prevent data error in the I2C bus between ICs, due to unstable operational voltage.